Means for controlling draft-air to boiler-furnaces.



L. 'DUFFNER. MEANS FOR CONTROLLING DRAFT AIR T0 BOILER FURNACES. APPLICATION FILED MAY 5, 1909.

Patented Feb. 1, 1910.

2 SHEETS-SHEBT 1.

IVVENTOR.

- Lucas Duff/var A T TORNE Y.

WITNESSES:

L. DUFFNER. MEANS FOR CONTROLLING DRAFT AIR T0 BOILER FURNACES.

' APPLIOATION FILED MAY 5, 1909.

Patented Feb. 1,1910.

2 BHEBTSr-BHEBT 2.

' .W/TNESSES: LVVE/VTOR. z w am Lucas Duff/ver- I I r x ATTORNEY.

LUCAS DUFFNER, OF ST. LOUIS, MISSOURI.

armor.

I Specification of Letters Patent.

MEANS'FOJR. CONTROLLING DRAFT-AIR 'I'O BOILER-FURNACES.

Patented Feb. 11, 191W.

Applicationfiled May 5, 1909. Serial No. 494,198.

To all whom it may concern:

Be it known that I, LUoAs DUFFNER, a

citizen of the United States, residing at St. Louis, State of Missouri, have invented certain new and useful Improvements in Means for Controlling Draft-Air to Boiler-Furnaces, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming a part hereof.

My invention has relation to improvements in means for controlling the distri bution of draft-air to boiler furnaces; and it consists in the novel construction and arrangement of parts more fully set forth in the specification and pointed out in the claims.

In the drawings, Figure l is a vertical longitudinal section of a conventional sectional boiler on the line 1-1 of Fig. 3, showing my invention applied thereto; Fig. 2 is a horizontal section von the line 22 of Fig. 1 parts being broken away; and Fig. 3 is a vertical transverse section on the line 51 3-3 of Fig. 1, the chain-grate however,

being removed, and other parts broken.

In the feeding of air to boiler furnaces employing mechanical stokers and chaingrates whereby the fuel is automatically 30 advanced from the front of the firebox to the rear thereof, a considerable volume of the air admitted to the fuel resting on such a grate passes through the ash or residuum portion of the fuel confined to the rear end of the grate, the comparatively slight resistance of such ash to the inflowing air current permitting the latter to pass freely therethrough into contact with the boiler thereby subjecting the boiler to undue cooling by the impact of the cool air against the boiler tubes or shell.

It is the object of my invention to utilize a part of the combustion products, diverting the same before they pass into the escape flue and lead them back into the space heneath that portion of the grate on which the ashes are supported, these products not only flowing into such space in opposition to the direction of flow of the cool air cur rent, but theirhigh temperature serving to materially heat the inflowing air so that the cooling of the boiler is eflectively prevented. Moreover by varying the velocity of influx of such opposing current of hot gases the grate area over which the cold inflowing air intended to support combustion, shall portions of the fuel which are not fully consumed, leaving only the hot furnace gases to pass up through the pervious layer of ashes, so that the danger of injurious cooling of the boiler is entirely eliminated.

The invention may of course be applied to any boiler furnace, and in the present instance 1 illustrate the samcnin connection with a sectional boiler of the Sterling type provided with a chain grate of conventional design.

The advantages of the invention will be best apparent from a detailed description thereof which is follows Referring to the drawings, 0! represents a series of drumsconnected by water tubes :6 forming conjointly a sectional boiler of the water-tube type, that shown being the conventional Sterling boiler. Such features as may be shown but to which no reference is madeare well known and require no description in the present connection. Mounted at the feed end. of the furnace is a chaingrate G, which automatically advances the fuel from the front to the rear of the firebox F, and in ordinary cases the fuel f remains unconsumed over approximately twothirds the area of the top of the grate, the

, rear third being covered with ashes a. The

ash layer is not only thinner than the fuel layer but is considerably more pervious to the air which passes upward through the front opening 0, through the grate to sup port the combustion of the fuel charge resting on the grate. Of course, the air thus admitted to the grate furnishes the necessary oxygen for supporting combustion, but a considerable portion of the air will pass freely through the thin ervious layer of ashes a before any consi erable heating of such air can take place, andthe comparatively cool air will thus pass through the ashes into the combustion chamber and against the boiler, thereby unduly cooling the same. By the use of my invention the portion of the air which would otherwise pass through the thin ash layer will be de-' distribute itself maybe accurately controlled .so that the air shall contact only with those flected or crowded toward the front portion of the grate or under the fuel-charge, and hence the deleterious effects of the cooling of the boiler is prevented.

The invention consists in utilizing the hot furnace gases to assist the general draft of the boiler, but in such a way that only these hot gases (and not the cool air) come in contact with the boiler.

Leading from the rear of the top of the combustion chamber is a return flue 1 which enters behind and below the bottom drum of the boiler, being tap ed behind such drum by a branch intakeue 2, Leading finally from the inner lower end of the flue 1 are branches 1', 1, which discharge at convenient points behind the rear end of the chaingrate G. The fiues 1 and 2 are provided with ordinary dampers e not necessary to describe in detail as they are common and well understood. The branches 1, 1 are provided at their discharge ends with hingeva'lves or dampers 3, each damper being coupled through a link 4 to an operating rod 5 passing through and out of the branch, and terminating in a handle or finger hold (3. Tapping the lower portion of theflue 1 is 1 a steam nozzle or lnjector 7 controlled by a valve 8, the steam being supplied thereto by g 'a steam-pipe 9 which takes its supply either yenting the inflowing cold air from Teaching a point beyond the rear edge of the uncon- Qsumed fuel-charge, the opposing gaseous current confining the air to the front of the grate, While the hot gases are free to pass through the layer of ashes a into the conibustion chamber, where in contacting with 'the boiler no deleterious effects can result.

Since the area occupied by the ashes a will vary with dlfferent kinds of fuel, and with the velocity at which the chain-grate may travel, the force with which the hot;

gases may be projected in opposition to the incoming air currents maybe carefully regof the damper 3.

ulated not only by a proper adjustment of the valve 8, but b regulating the position 11 Fig. 1, the air is shown by the "feathered arrows, and the hot gases by lain arrows, illustrating how the air is con "ned in its-flow to that portion of the grate occupied by the unconsumed fuelchargef.

Having described my invention, what I claim is:

1. In combination with a boiler furnace provided with a fire-box and a combustion chamber, a grate for. supporting and advancing the fuel toward the combustion chamber, means for admitting atmospheric air beneath the front of the .grate, a flue leading from the combustion chamber for returning and discharging a portion of the hot combustion products along the bottom of the rear of the grate and in a direction opposed to the general direction of flow of the atmospheric air, and a jet nozzle for projecting the returned combustion products under the section ofthe grate occupied by the ashes, substantiallyas set forth.

; 2. In combination with a boiler furnace provided with a fire-box and a combustion chamber, a chain grate for supporting the fuel and advancing the consumed portions thereof rearwardly, means for admittingatmosphcric air beneaththe front of the grate, a flue leading from the combustion chamber for returning and discharging a portion of the hot combustion roducts along the bo tom of the rear of t egrate and in adirection opposed to the general direction of flow of the atmospheric air, means for projecting the returned combustion products under the entire section of the grate occupied by the ashes, and dampers for controlling the products so projected, substantially as set forth.

In testimony whereof I aflix 'my signature,

in presence of two witnesses.

LUCA S DUFFNER.

Witnesses: 5

ERNs'r S'rARnN, Jos. A. MICHEL. 

